Matlab觀察者模式

要點：

1、服務端（Subject）維護一個觀察者的列表，以便能夠向所有的觀察者（Observer）推送信息

2、觀察者可以獲取服務端的狀態

3、服務端和觀察者可抽象，可以有多個不同實現

Subject.m

classdef Subject < handle
    properties(Access = private)
        observers = Observer.empty();
    end
    methods
        function add(obj,observer)
            obj.observers(end + 1) = observer;
        end
        function rm(obj,observer)
            index = [obj.observers] ~= observer;
            obj.observers = obj.observers(index);
        end
        function notify(obj)
            for i= 1:length(obj.observers)
                obj.observers(i).update(obj);
            end
        end
    end
end

ConcreteSubject.m

classdef ConcreteSubject < Subject    
    properties(Access = public)
        news
    end   
    methods
        function set.news(obj,news)
            obj.news = news;
        end      
        function news = get.news(obj)
            news = obj.news;
        end
    end
end

Observer.m

classdef Observer < handle & matlab.mixin.Heterogeneous
    methods(Abstract)
        update(~,~);
    end
    methods(Sealed)   
        function res = eq(obj1,obj2)
            res = eq@handle(obj1,obj2);
        end
        function res = ne(obj1,obj2)
            res = ne@handle(obj1,obj2);
        end
    end 
end

ConcreteObserver1.m

classdef ConcreteObserver1 < Observer
    properties
        name
    end    
    methods
        function obj = ConcreteObserver1(name)
            obj.name = name;
        end
        function update(obj,subject)
            disp([obj.name, ' has got subject news: ',subject.news]);
        end
    end
end

ConcreteObserver2.m

classdef ConcreteObserver2 < Observer
    properties
        name
    end
    methods
        function obj = ConcreteObserver2(name)
            obj.name = name;
        end
        function update(obj,subject)
            disp([obj.name, ' has received subject news: ',subject.news ]);
        end
    end
end

測試代碼：

sub = ConcreteSubject();
sub.news = 'hello matlab';
o1 = ConcreteObserver1('obs:a');
o2 = ConcreteObserver2('obs:b');
 
sub.add(o1);
sub.add(o2);
sub.notify();
 
sub.rm(o1);
sub.news = 'hello observer pattern';
sub.notify();